Screed assemblies for road finishers are known from practice. They are used for smoothing and compacting asphalt mixed material. For this purpose, they are pulled by a tractor unit of a road finisher. In case of modern road finishers, the screed assembly is generally pulled floating; this means that the screed is resting on the material to be smoothened and compacted and that the flotation and consequently, the thickness of the installed road surface are essentially adjusted by the pitch angle of the screed and the pulling speed.
It is known that one or more compacting devices are provided at screeds. Screed assemblies of the applicant comprise for example tamper bars, vibration units and/or pressure bars in various combinations.
Furthermore, screed assemblies comprising several screed segments are known. These for example can be extending segments of screeds, by extending of which, the working width of the screed assembly may be enlarged. Rigid attachment parts are likewise known.
At the beginning of an installation run, initially, the screed assembly is usually placed at a start point. This may be an aid, such as a wooden beam, on which the screed assembly is placed before the installation run starts. It may also be a straightly cut edge of an already existing asphalt surface layer, on which the asphalt layer to be newly installed is to be applied.
It may occur that several compacting units are arranged one behind the other in the direction of travel of the road finisher and consequently pass the transition between the aid or the straightly cut edge and the newly laid asphalt mix material one after the other. This may for example be a result of the fact that several compacting devices are arranged one behind the other on one and the same screed segment, or that screed segments with one or more compacting devices, respectively, are arranged one behind the other. Conventional road finishers simultaneously activate all compacting devices. In the event that all compacting devices are activated at the point in time, when the first compacting device passes the transition, this leads to the fact that the compacting devices, which have not yet passed the transition, strike the aid or the already hardened preceding asphalt layer and, thus, the existing asphalt layer or the compacting devices are damaged. In cases, in which all compacting devices are only activated, if all compacting devices have passed the transition, the initial sections of the newly laid surface remain unprocessed by the previous compacting devices. As recognized by the inventor, this may lead to inhomogeneities and, consequently, to variations in quality in the finished surface.